Raspberry PI Back To Base Home Alarm

Cormac O'Mahony

05 Jan 2025 — 2 min read

My raspberry PI project is a back to base add-on to a very old home alarm system. My goal is keep the existing panel functioning as is, extending its usefulness with the raspberry PI.

My aim is to get PI to do the following for me:

Monitor each of the motion sensors connected to the raspberry PI.
Monitor the indoor / outdoor sirens
Remotely disable sirens
Remotely enable / disable intruder monitoring
Receive a push notification when an intruder is detected
Log statistics on room usage
Live motion monitoring

Alarm Panel Motion Sensors

Raspberry PIFace Input Ports

Circuit Design

My circuit design was an exercise in trial and error. My first attempt was to connect the sensors directly to the input sensors on the Raspberry PIFace, the motion sensors go to ground when they sense movement, and the PIFace inputs also work on this premise so this seemed like a logical and very simple solution. The only problem with the approach is it impacted the existing alarm system, by connecting directly to the sensor input I could never arm the alarm panel. Wiring directly to PIFace puts the zone in a constantly open state.

Plan B was to use to the motion sensor to drive a transistor to switch the input on the PiFace by connecting the input to ground. My motion sensor outputs a 6v 4.2ma when nothing is happening, once motion is detected it goes to ground. To switch only when the current from the sensor is pulled down to 0v we need an NPN transistor.

The base of the transistor is connected to the output of the motion sensor. The collector is connected to the common ground and the emitter is connected to the input port on PiFace. When motion is detected the transistor is switched allowing current to flow from the input port to ground, triggering an input that can be read on the Pi.

The circuit allows the alarm panel to function normally, while also allowing PI to detect motion events using its inputs.

Remote Development With Codespaces

cal machine so you can work with a new repository? Is Docker hogging CPU and memory, killing the promise of all-day battery life? Sick of gigabyte image downloads consuming your mobile data plan? Are you having issues running Docker or Terraform on Apple silicon? Over dealing with machine-specific problems that

How To Use Spark Partitions With Postgres

In the post, we will explore how we can use partitions to reduce job execution time by increasing parallelism. Specifically, we will focus on building Spark partitions from tables in a Postgres database. Spark is an analytics engine for processing large datasets. Spark allows you to process enormous datasets across

Installing aws-azure-login on Apple M1

Aws-azure-login is a command-line utility for organisations using Azure Active Directory to authenticate users to the AWS console. It lets you use an Azure AD login (including MFA) from a command line to create a federated AWS session and places the temporary credentials in the proper place for the AWS

Building A Development Spark Cluster with Postgres Using Docker And Make

Overview My goal is to build a decent approximation of a production Apache Spark EMR environment for development and testing. For development, I need: * A Postgres database to persist datasets. * A Spark cluster with two worker nodes. * A Jupiter notebook server for prototyping. * To submit a PySpark job to the